belle | Belle , Bonne , Sage — music notation

belle is a C++ library. belle has no bugs, it has no vulnerabilities and it has low support. You can download it from GitHub.

Sheet music is represented in Belle using a graph. A graph is formally a list of nodes and a list of edges connecting the nodes. Graphs may take many forms. Belle uses a edge- and node-labeled multidigraph. A multidigraph has directed edges and multiple edges between nodes are permitted. The labels are key-value pairs where the key or value can be a MICA music concept (e.g. en:Value->en:C4), ratio (e.g. en:NoteValue->1/4), or string (e.g. "Text"->"Andante"). These graphs may be thought of as having structure (relationships between nodes content (information, i.e. labels on the nodes and edges). Since both the structure and content are generalizable, graphs are ideal for representing music notation. Adding nodes to a graph involves creating the nodes and connecting the nodes by edges. Accessing the graph structure and content is achieved by traversing the graph through its nodes and edges. Graphs may have multiple edges departing from a node, so filters are used to decide which paths to take during traversal. A filter is a label with partial information specified, and an edge is followed if the filter matches the edge's label. In Belle, a filter match occurs when the edge label contains all of the keys of the filter. The edge label may contain more information than the filter and still match so long as each item in the filter is found in the edge label. The main single-edge traversal functions are next and previous. These look for a single filter match and return the corresponding node if found. If more than one node matches the filter, then no node is returned and a multi-node traversal function must be used. The two main types of multi-node traversal are series and children. Series finds a path through the graph matching the filter. Intuitively it is like following next and building a list of the nodes it finds. However, it first backtraces with previous, so no matter which node in the path you call series on, it will return the same path. The children function builds a list of all the nodes that match the filter going in the forwards direction. Graphs do not store any notion of edge order. Therefore, though children will always return the same objects given the same input arguments and graph, the order of the objects in the returned array is necessarily indeterminate and can vary.